Pillar Formwork

ABSTRACT

A column formwork for use in concrete construction is described, including a planar member  1  constituting the formwork, and at least one connecting section provided for form-fit connecting two opposing edges  3, 3 ′ of the planar member ( 1 ) and thus for constituting a tube segment, wherein at least the connecting-section surface facing the planar member  1  exhibits a substantially constant curvature that substantially corresponds to the curvature of the tube segment.

This application is a continuation of U.S. application Ser. No.10/497,592, filed Jun. 3, 2004.

FIELD OF THE INVENTION

The present invention is directed to a column formwork for use inconcrete construction.

BACKGROUND OF THE INVENTION

Column formworks are used in concrete construction to build columns,supports, or similar concrete elements. Recently, in addition toconventional steel and wood formworks, wound formworks of sheet metal,cardboard, or synthetic material have increasingly been employed. In thecase of wound cardboard formworks, the outer formwork tube, whichprimarily serves to hold the formwork together, is constructed ofpaperboard or cardboard. After the column has been concreted and theconcrete has set, the outer formwork element is removed by tearing itopen by means of an integrated tear strip.

A column formwork comprising a multilayered wound flat material is knownfrom DE 295 18 077. The flat material is a polyethylene-coated papersheet. Due to the multilayered winding, paper layers and polyethylenelayers alternate in the wall of the formwork tube in this columnformwork.

DE 296 09 259 discloses a column formwork comprising a tube segmentdivided along its longitudinal axis. Connecting means are provided inthe area of the dividing line to hold the formwork together. Toconstruct this column formwork, a tube segment is slit open once alongits longitudinal axis. To ensure simple removal, it is recommended thatthe column formwork be constructed of a synthetic material that can bebent apart when removing the formwork. To the inside of the columnformwork is applied an auxiliary formwork material, which avoids formmarks resulting from the dividing line.

These known column formworks have various disadvantages in common. Forone thing, the formworks exhibit an extremely large volume, thus causingproblems, particularly during transportation, that are reflected in highcosts. The column formwork interior, provided for filling up withconcrete, is nothing other than dead volume during transportation, andthus only a very small quantity can be transported in each load. Thecolumn formwork according to DE 296 09 259 also exhibits this problem,as it involves shape-retentive synthetic material tubing that can bebent apart briefly with sufficient expenditure of force only duringremoval.

Moreover, the above-described column formworks are single-use products,as the outer formwork element is removed from the cured concrete bytearing it open. Reuse of the column formwork is thus excluded. In thecase of the column formwork according to DE 296 09 259, this problem issolved only partially. Although the outer part of the formwork can bereused, the necessary interior lining having e.g. a tube of thinpaperboard is a single-use product.

DISCLOSURE OF THE INVENTION

This is where the present invention begins. It is intended to provide acolumn formwork that can be reused and easily transported. According tothe present invention, this object is solved by the column formworkaccording to independent claim 1. Other advantageous aspects, details,and embodiments of the present invention are evident from the dependentclaims, the description, and the drawings.

The present invention is based on the idea of using, not, as previouslytypical, prefabricated tubes as column formworks in concreteconstruction, but rather planar members equipped with connectingsections, through which a form-fit connection of two opposing edges ofthe planar member is possible. The material comprising the planar membermust satisfy two conflicting conditions: on one hand, it must exhibitsufficient strength to withstand the pressure of the poured concrete,and on the other hand, it must exhibit sufficient elasticity to be ableto be bent into a tube with no difficulty. In particular, this tube mustremain dimensionally stable, that is, circular in diameter, under thepressure of concrete, that is, after the concrete is poured.

The column formwork according to the present invention for use inconcrete construction comprises a planar member constituting theformwork, and at least one connecting section, provided for form-fitconnecting two opposing edges of the planar member and thus for forminga tube segment, wherein at least the connecting-section surface facingthe planar member exhibits a substantially constant curvature thatsubstantially corresponds to the curvature of the tube segment. In thisway, it is achieved that the column formwork takes on a round shape. Ifconnecting sections having no curvature are used, the bent planar memberwould take on a slightly tear-shaped form and thus cause unsatisfactoryresults in the concrete parts. Slight differences between the curvatureof the connecting section and the curvature of the tube segment aretolerated within the context of the present invention, since acceptableresults can be obtained nonetheless.

The column formwork according to the present invention can betransported with no difficulty in large quantities in a flat statebefore bending it into a tube.

The use of the term “substantially constant curvature” is intended tomake clear that manufacturing-dependent deviations from a constantcurvature are, of course, tolerated, as long as they are not so markedthat the column formwork exhibits a diameter that deviates substantiallyfrom a circular diameter.

According to a preferred embodiment of the present invention, the planarmember comprises an elastic synthetic material. Such a material fulfillsthe two above-mentioned conditions especially well, namely sufficientshape-retentiveness after the concrete is poured and, at the same time,sufficient elasticity that allows bending into a tube with nodifficulty. Such a column formwork exhibits the great advantage that nosingle-use materials are provided, such as the typically used cardboard,thus facilitating multiple reusage of the formwork.

The two opposing edges of the planar member must be form-fit connectedtogether. To do this, at least two connecting sections are generallyused. Advantageously, each of these connecting sections is attached tothe planar member flush with one edge of the planar member. However, inthe context of the present invention, the connecting sections can, inprinciple, also be attached to the planar member at a short or even asomewhat long distance from the edges to be connected. In such a case,the tongues described below for connecting the connecting sections mustbe adjusted accordingly in their dimensions or e.g. replaced by flexiblebands.

However, an embodiment having just one connecting section attached nearan edge of the planar member and protruding over this edge is alsoconceivable. The part of the connecting section protruding out over theedge is then connected with the planar member near the opposing edgeafter the planar member is bent into a tube segment. This connectioncan, in principle, take place in any manner, for example throughglueing. However, the planar member can also exhibit e.g. projectionsthat engage in corresponding recesses of the connecting section and thusfacilitate a secure form-fit connection of the opposing edges.

Although the two above-mentioned conditions “stability of dimension” and“elasticity” are naturally fulfilled to a sufficient extent by a numberof materials that can, in principle, be used in any thickness, certainmaterials used in certain thicknesses yield particularly good resultsfor the purpose of very easy handling. For these reasons, both the useof fiber reinforced materials, of fiber reinforced synthetic materials,or of polyester, especially synthetic fiber reinforced materials, glassfiber reinforced materials, and carbon reinforced materials, especiallyglass fiber reinforced materials or carbon reinforced syntheticmaterials, especially fiber reinforced polyester, as the elasticsynthetic material, and a planar member having a thickness of 0.5 to 5mm, especially having a thickness of 1 to 4 mm, particularly preferablyhaving a thickness of 1.2 to 3 mm, are preferred embodiments of thepresent invention. Planar members having a thickness of 1.4 to 2.5 mmare particularly well suited, and those having a thickness of 1.5 to 2mm are most particularly preferred.

For reasons of reduced variety of form of the connecting sections, theconnecting-section surface facing away from the planar member canadditionally be provided with a substantially constant curvature, thiscurvature then differing from the curvature of the tube segment. In thisway, a connecting section can be used for column formworks of varyingdiameters.

Although the column formworks according to the present invention can beused for concreting columns of greatly varying diameters, and inprinciple even for concreting columns of any diameter, column formworkshaving a typical concrete construction diameter of 100 to 2000 mm,especially of 200 to 1000 mm, are preferred. Diameters of 200 to 450 mm,of 250 to 500 mm, of 500 to 900 mm, and of 600 to 1000 mm areparticularly preferred.

The connecting sections can be affixed to the planar member in variousways, namely e.g. through glueing, riveting, nailing, or welding.Glueing the connecting section and the planar member is particularlypreferred because doing so causes no visible traces in the finishedconcrete parts.

Column formworks having connecting sections that exhibit, in thedirection of the tube-segment tangent perpendicular to the tube-segmentaxis, an extension of 1 to 50%, especially 3 to 25% of the tube-segmentdiameter, are particularly preferred embodiments of the presentinvention. This ensures that, after the concrete is poured into theformwork, the connecting sections do not detach from the planar member.Pouring the concrete creates strong forces perpendicular to the formworkwall, and there is thus a risk of the formwork breaking apart along theplanar member edge held together by the connecting sections. To preventsuch breaking apart, the connecting sections must be appropriatelytightly connected together, and an appropriately strong connectionbetween connecting section and planar member must be ensured. For thisreason, connecting sections that exhibit, in the direction of thetube-segment tangent perpendicular to the tube-segment axis, anextension of 5 to 15%, especially of about 10% of the tube-segmentdiameter, are most particularly preferred.

In view of the above-mentioned column diameters typical in concreteconstruction, connecting sections that exhibit, in the direction of thetube-segment tangent perpendicular to the tube-segment axis, anextension of 10 to 100 mm, especially from 20 to 75 mm, are preferred.Connecting sections that exhibit, in the direction of the tube-segmenttangent perpendicular to the longitudinal axis of the tube segment, anextension of 30 to 50 mm, especially of 35 to 45 mm, are particularlypreferred.

In principle, the connecting sections can be constructed of any kind ofsufficiently dimensionally stable material. The connecting sections arepreferably constructed of synthetic material, and the connectingsections are particularly preferably constructed of polyester, of afiber reinforced synthetic material, especially of glass fiberreinforced synthetic material or carbon reinforced synthetic material,particularly preferably of glass fiber reinforced polyester or carbonreinforced polyester.

Most particularly advantageous characteristics result when theconnecting sections and the planar member comprise the same material. Inthis way, an especially simple and tight connection between the parts ispossible through glueing.

To ensure a secure, form-fit connection of the opposing edges of theplanar member, in the context of the present invention, it isparticularly preferred that the connecting sections extend in thedirection of the tube segment axis over the entire length of the tubesegment. In this way, the edges of the planar member can be form-fitconnected over the entire length of the column formwork withparticularly great strength and precision.

The connecting sections can, in principle, be mechanically connectedwith one another in any manner known in formwork engineering, thus forexample using clamps, wedges, locks, or bolts. In the context of thepresent invention, connecting sections that exhibit grooves and tonguesare preferred. To connect the edges of the planar member, one tongue ofone connecting section engages in a groove of the other connectingsection with a precise fit. The stable cohesion of the edges of theplanar member is ensured e.g. through a bolt that is guided throughbores in the connecting sections and then screwed down.

Another important condition for achieving good results in the form of anexcellent surface finish of the concrete columns is preventing water andcement paste from penetrating the formwork. At the junction of the edgesof the planar member, there is a risk that, in the case of aninsufficiently form-fit junction, water penetration and thus bleeding offine concrete components could occur at the seam. This can cause visibleunevenness on the surface of the concrete column. For this reason, aplanar member and connecting sections are preferably used whose edgesare especially smooth due to an appropriate subsequent treatment such asgrinding or polishing, and that facilitate a very good, preciselyfitting connection. Furthermore, according to a particularly preferredembodiment of the present invention, the tongues of the connectingsections are equipped with seals, thus preventing penetration of waterthrough the connecting sections.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is intended to be explained in greater detail below byreference to an exemplary embodiment in association with the drawings,wherein

FIG. 1 shows a cutaway of a cross-section through a column formworkaccording to the present invention;

FIG. 2 shows a part of a cross-section through a column formworkaccording to the present invention, having a larger diameter comparedwith the column formwork of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a cutaway of a cross-section through a column formwork. Theplanar member 1 is equipped with the connecting sections 2 and 2′, whichare each attached adjacent to the edges 3, 3′ of the planar member. Theconnecting-section surface 4, 4′ facing the planar member 1 exhibits aconstant curvature, the curvature substantially corresponding to thecurvature of the tube segment. In this way, it is achieved that thecolumn formwork takes on a precisely round shape. The connecting-sectionsurface 5, 5′ facing away from the planar member likewise exhibits aconstant curvature, the surface 5, 5′ of the connecting section shownbeing more sharply curved than the surface 4, 4′. The edges 3, 3′ of theplanar member 1 exhibit a highly precise fit. The connecting section 5is equipped with two tongues 6, while the connecting section 5′ exhibitstwo corresponding grooves. However, each of the two connecting sectionscan also be equipped with one tongue and one groove. The connectionbetween the two connecting sections and thus the positive connection ofthe two edges of the planar member results through an engagement of thetongues 6 in the corresponding grooves. The penetration of water throughthe connecting sections 2, 2′ is prevented by the longitudinally runningseals 7. The required securing of the connection through a clamp thatcovers the two connecting sections 2, 2′, or a bolt that is guidedthrough the two connecting sections 2, 2′ and then screwed down, is notshown.

FIG. 2 likewise shows a cutaway of a cross-section through a columnformwork. In FIG. 2, the extension t of connecting section 2 in thedirection of the tube-segment tangent perpendicular to the axis of thetube segment is emphasized.

List of Reference Numbers

1 Planar member

2, 2′ Connecting section

3, 3′ Edges of the planar member

4, 4′ Connecting section surface facing the planar member

5, 5′ Connecting section surface facing away from the planar member

6 Tongues

t Extension of a connecting section in the direction of the tube-segmenttangent perpendicular to the tube segment axis

1. A column formwork for use in concrete construction, comprising: asingle formation (1), said single formation comprising a glass fiberreinforced elastic synthetic material having a thickness of 1.4 to 2.5mm, and at least one connecting section provided for positivelyconnecting two opposing edges (3, 3′) of the single formation (1) andthus for forming a tube segment from the single formation; wherein atleast a connecting-section surface (4, 4′) facing the formation (1)exhibits a substantially constant curvature and the curvaturesubstantially corresponds to a curvature of the tube segment.
 2. Thecolumn formwork according to claim 1, characterized in that,additionally, the connecting-section (2,2′) surface (5, 5′) facing awayfrom the formation (1) exhibits a constant curvature, this curvaturediffering from the curvature of the tube segment.
 3. The column formworkaccording to claim 1, characterized in that the connecting section (2,2′) is constructed of synthetic material.
 4. The column formworkaccording to claim 1, characterized in that the connecting section (2,2′) is constructed of a polyester or of a fiber reinforced syntheticmaterial.
 5. The column formwork according to claim 1, characterized inthat the formation (1) and the connecting section (2,2′) consist of thesame material.
 6. The column formwork according to claim 1,characterized in that the connecting section (2, 2′) extends in thedirection of the tube-segment axis over the entire length of the tubesegment.
 7. A column formwork for use in concrete construction,comprising: a single formation (1), said single formation comprising aglass fiber reinforced elastic synthetic material having a thickness of1.4 to 2.5 mm, and two connecting sections (2, 2′) provided forpositively connecting two opposing edges (3, 3′) of the single formation(1) and thus for forming a tube segment from the single formation;wherein a connecting-section surface (4,4′) facing the formation (1)exhibits a substantially constant curvature and the curvaturesubstantially corresponds to a curvature of the tube segment.
 8. Thecolumn formwork according to claim 7, characterized in that,additionally, the connecting-sections (2, 2′) include a surface (5,5′)facing away from the formation (1) which exhibits a constant curvature,this curvature differing from the curvature of the formation (1).
 9. Thecolumn formwork according to claim 7, characterized in that theconnecting sections (2, 2′) exhibit, in the direction of a formation (1)tangent perpendicular to a formation (1) axis, an extension (t) of 1 to50% of the circumference of the tube segment.
 10. The column formworkaccording to claim 7, characterized in that the connecting sections (2,2′) exhibit, in the direction of a formation (1) tangent perpendicularto a formation (1) axis, an extension (t) of 5 to 15% of thecircumference of the tube segment.
 11. The column formwork according toclaim 7, characterized in that the connecting sections (2, 2′) exhibit,in the direction of a tube-segment tangent perpendicular to atube-segment axis, an extension (t) of 10 to 100 mm.
 12. The columnformwork according to claim 7, characterized in that the connectingsections (2, 2′) exhibit, in the direction of a formation (1) tangentperpendicular to a longitudinal axis of the formation (1), an extension(t) of 30 to 50 mm.
 13. The column formwork according to claim 7,characterized in that the connecting sections (2,2′) are constructed ofsynthetic material.
 14. The column formwork according to claim 7,characterized in that the connecting sections (2, 2′) are constructed ofpolyester or of a fiber reinforced synthetic material.
 15. The columnformwork according to claim 7, characterized in that the formation (1)and the connecting sections (2,2′) consist of the same material.
 16. Thecolumn formwork according to claim 7, characterized in that theconnecting sections (2, 2′) extend in the direction of the tube-segmentaxis over the entire length of the tube segment.